1. Field of the Invention
The present invention relates to differential pressure sensors with the transducing or sensing elements and the electrical leads isolated from the sensed pressurized fluids or media, without using separate isolating diaphragms.
2. Description of the Prior Art
Semi-conductor diaphragms that have resistors forming strain gage sensors disposed on the diaphragm surface are used for low-cost, accurate pressure sensors. The pressure media being sensed is usually corrosive, and thus isolating the sensing elements, circuitry, and the electrical connections from direct contact with the pressure media is desireable for reliable operation. Various isolation arrangements have been advanced, but they involve additional costs in construction of isolation sections in sensor housings in which separate isolating diaphragm members are mounted. Additional housings and additional diaphragms in order to obtain isolation increases the expense of manufacture and can reduce the accuracy of the sensor. An example of a miniature pressure transducer that uses a silicon diaphragm, with a silicon cover for absolute pressure measurements, and having a piezoresistive bridge formed by diffusion of resistors on the surface of one side of the diaphragm is shown in U.S. Pat. No. 4,023,562. The present invention discloses means for providing media isolation for sensors of this general type.